Hydrocarbon oil additive



United States Patent 6 HYDROCARBON OIL ADDITIVE John P. McDermott, Springfield, N. J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application August 25, 1951, Serial No. 243,767

5 Claims. (Cl. 260-243) The present invention relates to an improved class of additives particularly suitable for use in lubricating oils and to the compounded mineral oils and other hydrocarbon products in which they are employed.

This application is a continuation-in-part of my copending application Ser. No. 100, 741, filed on June 22, 1949, now U. S. Patent No. 2,610,182.

Modern developments in the design of internal combustion engines, with increasing engine speeds and compression ratios, have imposed a severe strain on the lubricants employed. In particular, the crankcase oil is raised to a high temperature and in the course of its circulation through the engine is repeatedly exposed to air under conditions highly conductive to destructive oxidation. Oxidative breakdown of the oil results in the formation of acidic products which corrode bearing surfaces and do considerable harm to the engine generally. Furthermore, the metallic corrosion products have the effect of catalyzing further oxidative breakdown of the oil.

A number of compounds, more especially those of the phenolic type, are known which exert an oxidation inhibiting effect when added to mineral lubricating oils and other hydrocarbon products. Their effect is to prevent oxidative breakdown of the oil both on storage (long potential reaction time and low temperature) and in use (short reaction time and high temperature). Although many antioxidants are known which stabilize the oil adequately on storage, the majority of them tend to break down with undesirable rapidity at high engine operating temperatures.

A principal object of the present invention is to provide a new class of lubricating oil antioxidants of good properties. Another object is to provide an antioxidant which is stable and effective at relatively high engine temperatures. Other objects and advantages will be apparent from the following description.

It has now been found, according to the present invention, that the salts formed by reacting thialdine or its homologs with xanthic and thioxa'nthic acids are extremely efiective antioxidants for hydrocarbon products liable to oxidation, especially mineral lubricating oils.

Thialdine, otherwise known as 5,6-dihydro-2,4,6-trimethyl-1,3,5-dithiazine, is represented by the structural formula net of acetaldehyde and ammonia with hydrogen sulfide. Thjaldine and the homologs of the same which are useful for the purposes of the present invention may be represented by the general formula where R represents an alkyl group of 1 to 10 carbon atoms. However, simple thialdine in which R is methyl is preferred.

Acids which may be used in forming the thialdine salts of the present invention include xanthic acids of the formula ROCSSH and thioxanthic acids of the formula RSCSSH and are represented by the general formula wherein X is selected from the group consisting of oxygen and sulfur and R represents an aliphatic radical having from 1 to 30 carbon atoms. The radical R may he saturated or unsaturated, straight or branched chain, with or without cycloaliphatic substituent chains, or it may be an alkyl substituted cycloaliphatic nucleus. Examples of suitable alkyl and alkenyl xanthic and thioxanthic acids are the lower acids such as isopropyl, nbutyl, n-oxtyl, noctylenyl, and n-decylenyl. Higher acids include dodecyl, hexadecyl, octadecyl, hexadecylenyl and the like. Mixtures of acids may be used. Aliphatic radicals having 220 carbon atoms are preferred. The most preferred products, however, are those prepared from the alkyl acids, both from the point of view of effectiveness and from the point of view of ease of preparation. The xanthic acids may be prepared by conventional means such as by reacting carbon disulfide with an alcohol or mercaptan having the desired hydrocarbon radical; usually the reaction is conducted in a KOH or NaOH solution of the alcohol or thioalcohol to prepare the stable potassium or sodium salt followed by hydrolysis to the xanthic acid by treatment with a mineral acid such as sulfuric acid. The acid may then be reacted with one mol of thialdine to give an addition product or salt.

The thialdine and homologous salts of the present invention may be readily formed by contacting the thialdine compound with the acid at a relatively low temperature such as 0 to 20 C. Since heat is evolved, the reaction is preferably conducted in the presence of 0 an inert solvent and by contacting the reactants gradually, usually at temperatures as low as 0 to 5 C. Suitable solvents include chloroform, carbon tetrachloride,

' by corrosion.

ethylene: dichloride, benzene, petroleum ether, and the like.

The following examples illustrate the preparation and testing of various thialdine salts according to this invention, but it. is to be understood that these examples donot limit the scope of the invention in any way-1 7 Example I.Preparation of thialdine isopropyl xanthate A solution of 34.8 grams (0.2 mol) of potassium isopropyl xanthate in 300 ml. of water was cooled to 5 C.

, after which 11.0 ml. of.50% H2504 (0.1 mol) was added dropwise with rapid stirring in a 1-liter, 3-necked flask equipped with a stirrer, thermometer, and reflux condenser. The reaction temperature was maintained at to 5 C.

A solution of. 32.6? grams. (0.20 mol). of thia'ldine in V 500 ml. of petroleum ether was then added dropwise over Example Il.Preparati0n of thialdine lauryl thioxanthate Lauryl thioxanthic acid. was. prepared by the method described in Example I, using 50.6 grams (0.16 mol) of potassium lauryl thioxanthate and 8.8. ml. of 50% H2504 (0.08 mol).

The thialdine salt was also-prepared by the method. described in Example I, using 26.8 grams (0.16 mol.) of. thialdine. A viscous yellow oil was obtained Whichupon analysis was found to cotnain 33.0%. sulfur, and 2.6% nitrogen.

Example 1Il;-Laboratory bearing corrosion tests In this test the additives were blended in 0.25% by weight concentrations in an extracted Mid-Continent oil of SAE grade and comparative tests run on these blends and on a sample of the unblended oil. The test was conducted as follows:

500 cc. of the oil was placed in a glass oxidation tube 13 inches long and 2% inches in diameter, fitted at the, bottom with a /4 inch air inlet. tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating bath so that, the oil temperature was maintained at 325 F. throughout the test. T'wo quarter. sections of automotive bearings; of copper-lead alloy, of known weight and having a total surface area of sq. cms., were attached to opposite sides of a stainless steel rod which was then immersed in. the test oil and rotated at 600 R. P. M., thus providing sufficient agitation of the oil during the test. Air was then blown through the oil at the rate of 2 cu. ft; per hour. Atthe end of each four-hour period, the bearings wereremoved, washed with naphtha, and weighed to determine the amount of loss The bearings were then repolished (to increase the severity of the test), reweighed and then subjected to the test for additional four-hour periods in like manner. The results are given in the following table ascorrosion life, which indicates the number of hours required for the bearings to lose 100 mgs. in weight, determined by'interpolation of the data obtained in the various periods.

Corrosion Thialdine Salt Life (hrs) Example IV.Laus0nengine test To confirmv the results of. laboratory test under; actual p r i g. c n i ions, a iunther: t s was runv using.

Cir

an SAE 30 extracted Coastal oil containing 0.25 weight percent of the thialdine isopropy-l xanthate of Example I as crankcase lubricant in a- Lauson engine. The operating conditions were 295 F. jacket temperature, 300 F. oil temperature, and 1800 R. P. M. at 1.5 indicated kilowatt load, and the duration of the test was 20 hours. At the end of the test the loss inweight of the copper-lead bearings was'determined- A blank test wasrun for comparison, using the base oil alone. The results ofthe test are shown below.

IYveiglht V 'OSS BI 01 Bearing Base all alone 250 Blend 20 From the preceding examples it will be evident that the thialdin'e salts of the present. invention are effective, antioxidants for lubricating oils.

As previously stated, ny of thealkyl" homologs; of. thi'aldine may be employed. although thialdine. itsellfI preferred.

The additives may' be blended in the oil in amounts of from about'0102 to 5% by weight, 0.5 to 2% being,

the preferred range. For loadabearing purposes. quantities of 2 to 15% maybe used. For handling. and storage, concentrates containing 15' to 5.0% or more may be prepared. These may be" added to basestocks to give. blends of the' desired concentration.

l'nadditionto the additives of this invention there may also be addedto" the oil other conventional. additives. including detergent type additives, such as metal soaps, metal petroleum sulfonates, metal phenateis, metal alcoholates, metal alkyl phenol sulfides, and the like. Examples of such additional additives are barium tert;..-octyl phenol sulfide, calcium tert-amyl' phenol sulfide, cadmium or nickel oleates, calcium phenyl' stearate, aluminum naphthenate, and zinc methylcyclohexyl thiophosphate.

The. lubricating oil base stocks used may be straight. mineral. lubricating oils or distillates derived from any suitable or desiredcrud'es, or, if desired,blended-loilsmay be employed. The. oil's may have been subjected to any conventional refining treatment such as acid, alkali and/- or clay treatment, or solvent extraction. Synthetic oils such as those prepared by the polymerization of olefins or' by the Fischer-Tropsch synthesis. or those of the. well known ether and ester type may alternatively be em; ployed, alone, mixed, or in combination with mineral oils.

Further types of additives which may, be, presentif de; sired include dyes, pour point depressants; heat thicken'ect fattyoils, sulfurized' fatty oils; organo-metallic compounds, sludge di'spersers, thickeners, viscosity index. improvers, o'iliness agents, vol toliz ed fats, wax es, or oils, and colloidal solids such as graphite or zinc oxide, etc. Solvents v and assisting agents such; as, esters, ketones, alcohols, aldehyd'es, and halogenated ornitrated. hyd'ro.. carbons may also be employed where necessary or die..- sirable.

Particularly suitable assisting agents are the C8 and higher alcohols (preferably (33 to C12) such as lauryl and stearyl alcohols, and the Oxo alcohols of corresponding chain length.

In addition to being employed in lubricants, the additives of the present invention: may also be employed in other hydrocarbon products susceptible to oxidative breakdown.

Among these may be mentioned motor' fuels, burning oils, mineral oil base hydraulic fluids,

in other products containing hydrocarbon oils as ingredi- 5. The process which comprises reacting a compound ents. of the general formula What is claimed is: R 1. As a new composition of matter the salt formed by reacting a compound of the general formula 5 E s s R R-H (311-42 H 10 H where R is a C1 to C10 alkyl radical, with an acidic sub- R E H R stance selected from the group consisting of xanthic and N thioXanthic acids at a temperature in the range of to 20 C. and in the presence of an inert solvent.

References Cited in the file of this patent where R is a C1 to C alkyl radical, with an acidic com- UNITED STATES PATENTS pound of the general formula R'XCSSH where R is 2,084,011 Teppema J 15, 1937 selected from the group consisting of C1 to C30 aliphatic 2,109,158 Teppema 22, 1933 hydrocarbon radicais and X is selected from the group 2,273,664 searle Feb 17, 1942 consisting of Oxygen and sulfur- 2,439,734 Himel et a1 Apr. 13, 1948 2. A new composition of matter as m clam] 1 Where- 2,610,182 McDel-mott Sept 9, 5 in R represents a monovalent aliphatic hydrocarbon radical of 2 to 20 carbon atoms. OTHER REFERENCES 3. Thialdine isopropyl xanthate.

Hackhs Chem. Dictionary, 3rd ed., page 848. 4. Thialdine lauryl thioxanthate. 

1. AS A NEW COMPOSITION OF MATTER THE SALT FORMED BY REACTING A COMPOUND OF THE GENERAL FORMULA 